Sheet metal working machine

ABSTRACT

A sheet metal working machine with a worktable has a ram which is controlled by at least two actuating and guiding elements, each fitted with a cylinder and a pressure-operated piston. The piston in each element has two separated working surfaces of different sizes. Each actuating and guiding element has a control organ which acts on the pressure of the individual piston surfaces in accordance with the eccentricity of the load on the ram. Fluid pressure may be used to operate the piston and the control organs may be programmed for regulating the feed of the pressure fluid.

United States Patent Hanni 1 -May 23, 1972 [54] SHEET METAL WORKING MACHINE 2,377,007 5/1945 Hess 100/258 R [72] Inventor: Eduard Hanni, Zofingen, Switzerland FOREIGN PATENTS OR APPLICATIONS [731 Assignee Maschinenfabfik Zmfin 717,505 10/1954 Great Britain 100/46 gen, Switzerland [22] Filed: May 4, 1970 Primary Examiner-Charles W. Lanham Assistant ExaminerGene P. Crosby [21] Attomey-Abraharn A. Saffitz 301 Foreign Application Priority Data 57 ABSTRACT May 28, 1969 Austria ..5078/69 A sheet metal working machine with a worktable has a ram which is controlled by at least two actuating and guiding ele- US. Cl- A ments each fitted a ylinder and a p essure.operated [51] Int. Cl. l ..B2lj 9/20 piston The piston in each element has two Separated working [58] Field of Search ..72/44l, 453, 447, 21, 386, Surfaces f m i Each actuating and guiding element 72/389; 100/258 258 46 has a control organ which acts on the pressure of the individual piston surfaces in accordance with the eccentricity of [56] References Cned the load on the ram. Fluid pressure may be used tooperate the UNITED STATES PATENTS piston and the control organs may be programmed for regulating the feed of the pressure fluid. 2,309,944 2/ 1943 Flowers 100/46 2,343,167 2/1944 Bench "100/258 A 4 Claims, 1 Drawing Figure PATENTEDMAY'23IQ72 I 3,664,174

INVENTOR EDUARD HAN ATTORNEY SHEET METAL WORKING MACHINE The present invention relates to a sheet metal working machine with a worktable and a ram, the latter being under the influence of at least two actuatingand guiding elements, each one equipped with a pressure cylinder actuated by a piston under pressure.

Sheet metal working machines are often equipped with a fixed guiding pillar arranged on both sides of the worktable, this pillar housing the movable ram and where the guiding pillars also accommodate the actuating elements. The pillars therefore assume the function of a guiding as well as an actuating element. With an asymmetrical load on the ram, it can easily happen that it is no longer moving parallel to the worktable, but that the guiding pillars are deflected, whereby an accurate machining of the workpiece is rendered impossible, bringing about the damaging of the machine. If, for instance, a workpiece is set-up at the edge of the ram and the machine is set in motion, the actuating element at the other side of the workpiece meets less resistance and covers a greater distance than the actuating element adjacent to the workpiece. In view of the elasticity of the materials used in construction, the guiding pillar next to the workpiece is particularly subject to bending stresses and this may even lead to seizing of the ram. If, then, the guiding element with a smaller load would be actuated to a smaller extent, i.e. in the case of a hydraulic piston under lower pressure, this bending efiect could be avoided. As an additional feature, it should be pointed out that this greatly depends on the exact positioning of the workpiece and its shape.

The invention therefore aims at designing a sheet metal working machine of the above described type which automatically compensates any deformation of the guiding elements over and above a certain range of tolerance. According to the invention, this is achieved by a piston in each one of the actuating and guiding elements having at least two separate working surfaces of different size and in separate spaces and that each actuating and guiding element is provided with a control organ, whose action is a function of the eccentricity of the load on the ram and controlling the pressure applied on the individual pistons.

By way of an example, the enclosed drawing shows the sheet metal working machine as per invention in a front view, in which the left-hand actuating and guiding element is cut open.

The sheet metal working machine according to the invention has a worktable l rigidly connected to the right and to the left with one actuating and guiding element 2a and 212 each. Furthermore, a ram 3 is provided, which is located on the two guiding and actuating elements in a movable manner in longitudinal direction. At the lower end of the ram 3, a bending tool 4 may be affixed, for instance, operating in concert with the bending tool 5 mounted on the worktable.

On both sides of the worktable l, a fixed guiding sleeve 6 is mounted, whereas ram 3 is supported by one movable guiding sleeve 7 each. The guiding sleeves 6 and 7 are mounted co-axially on the guiding sleeve 8, and where the guiding sleeve 7 is held by means of non-illustrated bushes in an axially displaceable manner. The inside of the guiding pillar 8 houses a piston 9 which rests against a dog 10. This dog 10 extends across axial slots in the guiding pillar 8, which are not illustrated and is lodged in corresponding cut-outs in the movable guiding sleeve 7.

The piston 9 has an axial bore 11 which is closed at one end, in which an axial extension 13 is located, forming a fixed part of cover 12 closing the guiding pillar 8. This cover is provided with a centrally located bore 14 passing through and extending through the whole extension, as well as an eccentric through bore 15 located beside the extension. In this manner, a first working surface 16 of smaller dimensions is formed inside bore 1 1 on the surface of piston 9, as well as a second, circular surface 17 of larger dimensions, separated from each other by a pressure seal 18. The center bore 14 is the inlet for the pressure fluid to the first working surface 16, whereas through the eccentric bore 15, pressure fluid 17 is admitted to the second working surface.

On the outside of the movable guiding bush 7, a bar 19 extending in a downward direction is rigidly fixed, having at its lower end a number of switches 20a and 20b In the example illustrated, three switches 20a are fixed to the lefi-hand side and three switches 20b are fixed to the right-hand side of the bar. These switches are in connection with an electro-hydraulic control loop which is not illustrated, the latter regulating the feed of the pressure fluid to the actuating elements.

The machine is operating as follows:

First case.

A workpiece is symmetrically arranged underneath the ram. Both pistons receive pressure fluid through bores 14 and 15, the ram is lowered in a perfectly parallel manner until it touches the workpiece. By the symmetrical distribution of the load, the two actuating elements are meeting the same resistance, they move to the same extent in a downward direction and the bar 19 remains perfectly vertical without triggering one of the switches 20a or 20b Second case.

The workpiece below the ram is slightly displaced to the right. Again, both bores 14 and 15 are open with the piston receiving the full pressure, until the ram touches the work piece. At this moment, the left-hand actuating element meets less resistance than the right-hand one as a result of the asymmetrical load and consequently, it continues its travel in a downward direction further than the right-hand actuating element, so that ram 3 takes up an oblique position. This results in a certain bending action of the pillars, the bar 10 deflects at its lower end slightly to the right and triggers the first of the switches 20a This stops the feed of the pressure fluid through bore 14 on the left-hand actuating element. By this action, only the second working surface 17 of piston 9 is in action, so that the pressure exerted on dog 10 becomes smaller. The right-hand actuating element continues to receive the full pressure on both working surfaces 16 and 17. The asymmetrical load is thus compensated, the ram 3 resumes its exactly parallel position relative to the worktable and the guiding pillars 8 are no longer bent.

Third case.

The workpiece is located still further to the right, approximately in the position shown on the drawing. In the starting position, both pistons 9 again receive the full pressure on the working surface, until the ram takes up its oblique position. In a manner similar to'the second case above, the first of the switches 20a is at first actuated, stopping the feed of the pressure fluid to the smaller working surface 16. Since, however, this in insufficient for compensating the oblique position, the next switch 20a is also triggered, which stops the pressure fluid through bore 17 and simultaneously, re-admits the feed to the smaller working surface 16 through bore 14. Here, only the smaller working surface 16 at the left-hand piston is still under pressure, and which is adequate to compensate the oblique position of ram 3.

Fourth case.

The workpiece is at the extreme right-hand end of ram 3. The pronounced deflection of the guiding pillar has the effect that successively, as in case 2, the feed to the smaller working surface 16 is interrupted, then, as in case 3, access to the smaller working surface 16 and the stoppage of the feed to the larger surface 17 and finally, as this proves inadequate for compensation of the deflection, the complete interruption of the feed to piston 9 of the left-hand actuating element. Consequently, only the right-hand actuating element is still in operation and ram 3 resumes its parallel motion relative to worktable 1.

With an asymmetrical positioning of the workpiece to the left, the feed of the pressure fluid to the right-hand actuating elements will be throttled, resp. interrupted in an analogous manner.

There are precisely seven points at which the workpiece may be set-up without causing the slightest deflection of the pillars 8 and consequently, an oblique position of the ram. In the intermediate positions between these seven points, a minimum deflection takes place which may generally be tolerated. Of course, there may be a possibility of subdividing the working surface of piston 9 into more than two partial surfaces 16 and 17, so that actually, more than seven points will be available, in which an exact compensation of the oblique position of the ram may be obtained. By subdividing into three partial surfaces, there are for example 15 points available for perfect compensation which, in most cases, may prove adequate. In order to achieve this subdivision into three partial surfaces, piston 9 may be provided with a second axial bore of smaller diameter, into which a second, axial extension bar is entering and which in turn is fitted to the tip of extension 13. The bore would then have to be positioned slightly off center and a further axial bore would be required for the pressure fluid inlet to the third working surface.

The feed control of the pressure fluid for the various working surfaces of piston 9 may also be realized in a different manner:

Instead of the full width tools 4 and 5 a number of different tools are set-up along the ram,so as to perform a number of consecutive operations on a small workpiece, a programmed control the pressure oil feed will be appropriate. If, for instance, the first machining operation takes place at the lefthand end of the ram, the programmed control will provide pressure feed to the left-hand actuating element. The lifting of the ram 3 then switches the programmed control one step further, so that at the next sequence of operations with the adjacent tool, the left-hand actuating element will receive the full pressure, while the right-hand actuating element is working only with a smaller surface. The programmed control will continue in a similar manner until finally, at the last step in the sequence of operations at the right-hand end of the ram, only the right-hand actuating element is fed with pressure oil. In a preferred form of carrying out the invention, the individual tools will be set-up at points of the ram, resp. worktable, at

which the deflection of the pillars will be accurately compensated. With this mode of operation, either the bar 19 with the switches 20 a and 20b will be left out, or simply be put out of action, so that the machine can be used for both operational methods.

I claim:

1, A sheet metal working machine with a worktable and a ram, in which the ram is under the influence of at least two actuating and guiding elements, each one fitted with a cylinder and a pressure operated piston, wherein the piston (9) in each of the actuating and guiding elements features two separated working surfaces of different size (l6, l7) and that to each actuating and guiding element, a control organ is allocated, acting to regulate the pressure on the individual piston surfaces in accordance with the eccentricity of the load on ram 3.

2. A sheet metal working machine according to claim 1, wherein the piston (9) has an axial bore (11) closed at one end, into which is extending and extension bar (13) having a diameter corresponding to the bore (1 l said cylinder having a front wall (12), said extension bar being fixed to the front wall of the cylinder; the extension bar (13) having an axial through bore for admitting pressure fluid.

3. A sheet metal working machine according to claim 2, wherein the front wall of the cylinder is facing the working surface of the piston (9) and is provided with an eccentric bore (17) for admitting pressure fluid.

4. A sheet metal working machine according to claim 1, wherein the ram is provided with a firmly fixed bar (19) extending in a downward direction, and where, within the range of the lower end of said bar (19) a number of switches (20a, 20b are actuated whenever the ram takes up an oblique position. 

1. A sheet metal working machine with a worktable and a ram, in which the ram is under The influence of at least two actuating and guiding elements, each one fitted with a cylinder and a pressure operated piston, wherein the piston (9) in each of the actuating and guiding elements features two separated working surfaces of different size (16, 17) and that to each actuating and guiding element, a control organ is allocated, acting to regulate the pressure on the individual piston surfaces in accordance with the eccentricity of the load on ram
 3. 2. A sheet metal working machine according to claim 1, wherein the piston (9) has an axial bore (11) closed at one end, into which is extending and extension bar (13) having a diameter corresponding to the bore (11), said cylinder having a front wall (12), said extension bar being fixed to the front wall of the cylinder; the extension bar (13) having an axial through bore for admitting pressure fluid.
 3. A sheet metal working machine according to claim 2, wherein the front wall of the cylinder is facing the working surface of the piston (9) and is provided with an eccentric bore (17) for admitting pressure fluid.
 4. A sheet metal working machine according to claim 1, wherein the ram is provided with a firmly fixed bar (19) extending in a downward direction, and where, within the range of the lower end of said bar (19) a number of switches (20a, 20b ) are actuated whenever the ram takes up an oblique position. 